I learnt from early on that logging out to take a break while in locations marked with the 'solo' icon would kick me out of the area and have me start from the beginning. Fair enough, don't understand why, but I avoid it if I can.
However, I'm in the middle of the 'Lightless Remnant' quest, which has no solo marking. After going through the first and middle tiers of the doomcrag, and logging out for lunch before the last step, I found on logging in that I was back outside the first tier, and that I couldn't simply sprint to the last one, but the quest order of events had actually reset itself to the first tier, and this is quite painful ; although it's only a few minutes combat, there is a lot of chit chat between characters.
I'm not interested in ranting or requesting the reason for that issue, as this would be unproductive ; but I would like to know when this happens, essentially, as in the solo locations, to know when I should avoid logging out at risk of having to redo previous quest events.
Cheers.